This invention relates to an apparatus for folding flat piece laundry and including folding control means for calculating the position of a laundry on the conveyor of the folder and also calculating where the fold is to be made and activating the folding means to make a series of folds at the proper position so that the laundry piece is folded into a smaller, symmetrical size. The application also discloses a method for calculating the position of the laundry piece on the folder conveyor and calculating the position where the folds are to be made.
Folders of the general type disclosed herein are used primarily in large industrial and commercial institutions such as hospitals, colleges, military bases and hotels where large quantities of flat piece laundry are washed and folded. By "flat piece laundry" is meant primarily sheets, pillow cases, bed spreads, towels and other similar items which are, for the most part, symmetrical in shape and can be ironed and folded by automatic equipment without manual handling. However, the invention disclosed in this application is not so limited and would have application on folders designed to fold other types of fabric structures.
In general, a folder receives a flat piece of laundry from an ironer and through manipulation by mechanical or pneumatic means folds the flat laundry piece into several successive smaller sizes to form a neat, easily handled bundle. Since the laundry pieces are ordinarily handled by the machine without manual assistance, some automatic means is necessary to tell the machine when to make each fold. Unless the fold is made at the proper place, the edges and seams on opposite sides of the fold do not match and further processes in the folder may therefore carried out improperly. In addition, mismatched edges and seams result in a ragged, unneat package which requires more space for stacking and storing. The problem is made somewhat more difficult because the flat piece laundry, for example, a sheet, of a given nominal size may be several percent larger or smaller than the average size. Even a relatively small variation can cause a drastic change in the appearance of the folded piece if not compensated for. While variations in laundry piece size may be minimized to some extent it is virtually impossible to eliminate them because they occur for a variety of reasons, including size variation when manufactured, stretching or pulling as a result of previous washing or ironing processes and repairing rips and tears. Therefore, some means must be provided on a folding machine to determine where the fold is to be made on each laundry piece given the assumption that the fold position may be slightly different from one piece to the next.
The typical system presently in use involves sensing the present or absence of a laundry piece at a particular point on the folder conveyor. The sensor, which may be a photocell or some similar device, actuates a timer set to the surface speed of the belt. Passage of the laundry piece within the scan of the sensor activates a timer, which given the surface speed of the belt, predicts a time at which the fold point of the laundry piece will be in position for the fold to be made. There are a number of difficulties with this approach. First, the measurement of the laundry is only approximate. The accuracy of the measurement is further degraded because the timer is based on a set belt speed which may vary slightly even under ideal conditions. Furthermore, when the belt speed is changed the timer and all of its associated mechanics must be reset. Because of the difficulty in prior art systems of constantly resetting timers based on changing laundry piece sizes and belt speeds, folders are typically run at a set speed which is somewhat faster than the fastest ironing rate. The ironing rate varies greatly for different types of flat piece laundry. For example, flat polyester and cotton sheets can be dried and ironed very quickly because the polyester is hydrophobic and the sheet has therefore absorbed less moisture than an all-cotton sheet. Likewise, laundry pieces having a double thickness, such as pillowcases, require a slower ironing speed because of the greater thickness of moist fabric which must be dried for a given amount of ironer surface area. The speed of the ironer is very easily changed to account for different types of laundry pieces and fabric constructions. A substantial problem results, however, when an ironer processing, for example, pillowcases and therefore running at a relatively slow speed discharges the laundry pieces onto a folder running at a much faster rate. Static electricity often builds up on the dried fabric. If the laundry piece comes out of the ironer somewhat crooked, the piece is pulled sideways since the side to exit the ironer first is grabbed and pulled at a much more rapid rate that the other side which is still in the ironer. This creates wear and tear on the fabric as a result of its being jerked out of ironer. The net result is a lower quality fold because of less precision in handling the laundry piece. There are other disadvantages in the prior art system as well. Running the folder at a constant high speed to avoid having to make frequent speed changes causes greater wear and tear on the machine, consumes more power, creates a higher noise level and can result in more injuries to operators.
Another factor which prior art folders have not taken into account is that slippage very often occurs while the laundry piece is being processed by the folder, especially if the trailing end of the laundry piece is still in the ironer. In order to produce an accurate fold, some compensation for slippage of the laundry piece within the folder must be made.